Method of treating metals



Patented Apr. 1, 1930 STATES CARTER HENRY ANDERSON, 01? OAK PARK,ILLINOIS, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEWYORK, N. Y., A CORPORATION OF NEW YORK . METHOD OF TREATING METALS NoDrawing.

This invention relates to methods of treat ing metals and has for itsobject the provision of a method of treating metals which when employedresults in the production of 5 ingots or castings which possesscommercially enhanced properties, such as toughness, desirablecrystalline structure, freedom from blow-holes, etc.

In carrying out the object of the invention,

1 in one embodiment thereof,metal, such as an alloy of palladium andcopper, is melted under controlled conditions and allowed to solidify.The solidified material produced by the above operations is thenremelted under controlled conditions of another character and the moltenmaterial cast into either an ingot or a casting. The cast materialresulting from the above treatment will have a desirable crystallinestructure and will be free from other conditions, such as the presenceof large blow-holes, which would render it commercially unsound, whichcharacteristics would not be present if the material were not remeltedunder altered conditions.

The invention will be clearly understood from the following detaileddescription of a specific application of the method to the production ofa contact alloy composed of approximately. 60% palladium and 40% copper,which is especially useful for the production of contact members to beused in electri' cal apparatus.

In this embodiment of the invention either an alloy of the desiredcomposition or the constituentmetals in the proper proportions areplaced in a graphite crucible and melted in a suitable furnace in areducing atmosphere to prevent the formation of oxides and theirassociation with the molten metals. Among the numerous reducingmaterials which may be used to supply a reducing atmosphere around'thealloy being treated in the melting step, which has just been described,the; preferred one is a mixture of carbon monoxide and carbon dioxide,in which the carbon inonoxide acts as a reducing agent and the carbondioxide is'inert. Other reducing materials which may be used arehydrogen and pro-,

ducer gas. The molten material is then pouredinto an ingot mold withoutany at- Application filed March 31, 1927. Serial No. 180,066.

tempt being made to prevent occlusion of the reducing gases by thematerial and the material-is allowed to solidify in the mold. Anexamination of material which has been treated in the manner justdescribed will show that the material is full of large blow-holes whichresult from the absorption of gases by the material and which rendercastings containing them commercially unsound.

The ingot produced by the above operations is placed in a non-reducingcrucible com posed of a material other than pure graphite, such asmagnesia, lime or zirconia, and the material is heated in a non-reducingatmosphere, such as air, until the material is molten and until theresultant vigorous evolution of entrapped or dissolved gas ceases. Whenthe material becomes molten and the evolution of gas ceases, thematerial is immediately poured into an ingot mold and allowed tosolidify, after which it may be worked in any desired manner to producecontact members therefrom.

An examination of the material resulting from the final treatmentoutlined above will show that it has a very *desirable crystal structureand that 'it is free from numerous large blow-holes. An ingot havingthese characteristics is considered commercially sound and may bereadily worked into articles having desirable physical properties.

Where it is desired to produce an article by casting directly from themolten state, it is advantageous to treat the material to be cast insuch a manner that the material will when solidified have what is termeda modified type of crystalline structure. By the term modifiedcrystalline structure is meant a crystalline structure obtained in amaterial cast directly from the molten state without subsequent workingor heat treating and which is very fine as compared to an uninterruptedgrain growth from the outside toward the center of a cast section.

It has been found that by properly controlling the conditions underwhich the last melt is made in the above described process, the metalwhen solidified will have a modified type of crystalline structure andthat material produced by the above described operunder the usualconditions under which they ill) ations may be cast directly into thedesired form to produce castings which will not fail are intended to beused.

Insteadof melting the material in a graphite crucible and casting itinto an ingot before the final melt and casting, the material may bemelted in a non-reactive crucible under reducing conditions, allowed tosolidify in the crucible and remelted in the same crucible undernon-reducing conditions until the evolution of gas ceases and then castinto an ingot as described above. Such material will also possessdesirable physical characteristics and will be free from objectionablevoids resulting from absorbed gases.

It is, of course, to be understood that the invention is-not limited tothe use of the above described method With a palladium-copper alloy ofthe exact composition stated above,

' but is equally applicableto palladium-copper .1 found that commerciallead may be improved by remelting it under conditions different fromthose from which it was solidified in the last stage of the smeltingoperations. This,

example illustrates the important feature that the invention applies tothe removal of deleterious conditions in metals other than the presenceof blow-holes or voids, for it is believed that the lead is freed by theabove mentioned process from oxides or other com- 1 pounds which arepresent insmelted lead and whiah are objectionable when pure lead isdesire It is also to be understood that the invention is not limited toa method wherein the material is melted in a reducing atmosphere andremelt'ed under, non-reducing conditions, but the invention embraces.any method in which metallic material is melted under one set'ofcontrolled conditions, is allowed to so- 1i ify and is remeltednndercontrolled condi ions different from those under whichthe first melt ismade.

-The terms metallic material or metal as used. hereinbefore and in theappended claims are intended to embrace commercially pure metals andalloys of two or more metals.

at is claimed is: Y

I 1. A method of treating metals, which con in melting a metal in thepresence of T u-a' reducing material, allowing the metal to solidify,and remelting the metal in the presence of a non-reducing material.

2. A method of treating metallic materials, which consists in melting ametallic material in a reducing atmosphere, casting the material into aningot, remelting the material: in a non-reducing atmosphere, and re-Xcasting the material.

3. -A method of treating metallic materials having the property ofabsorbing gases while in the molten state, which consists in melting ametallic material of said type in a reducing atmosphere, allowing thematerial to solidify, remelting the material in a nonreducing atmosphereto cause an evolution of gas from the material, heating the materialuntil the evolution of gas substantially ceases, and casting thematerial.

4. A method of treating metallic materials,

which consists in melting a palladium con-- taining material underreduclng conditions, allowing the material to solidify, and remeltingthe material under non-reducing conditions.

5. A method of treating metallic materials,

which consists in melting a palladium-copper. alloy in a reducingatmosphere, allowing the alloy to solidify, remelting the alloy in anon-reducing atmosphere, and casting thealloy into an ingot.

6. A method of treating metals, which consists in melting an alloycomprising substantially 60% palladium and 40% copper under reducingconditions, casting the alloy into an ingot, remelting the alloy undernon-reducing conditions to cause an evolution of entrapped gases,maintaining the alloy in a molten state until the evolution'of gasessubstantially ceases, and recasting the material.

7. A method of treating metals, which consists in melting a metal underreducing conditions, allowing the metal to solidify, and

remelting 'ditions.

8. A method of treating metals, which consists in melting a metal in areducing atmosthe metal under non-reducing conphere, allowing the metalto solidify, and remelting the metal in air.

9. A method of treating metals, which consists in melting a metal in thepresence of carbon monoxide, allowing the metal to solidify, andremelting the metal in air. j 10. A method of treating metals, whichconsists in meltin a metal in a reducing atmosphere in a re ucingcrucible, casting the metal, remeltingthe metal in air in a nonreducingcrucible, and recasting the metal. 11. A method of treating metals,which consists in melting a palladium-copper alloy in the presence ofcarbon monoxide, casting the alloy into an ingot, remelting the alloy inair to cause the evolution of entrapped gases, and recastin thematerial.

12. A method ot treating metals, which.

consists in melting a palladium-copper alloy comprising substantially60% palladium and 40% co per in a graphite crucible in the presencecarbon monoxide, casting the alloy into an ingot, remelting the alloy ina nonreducing crucible in the presence of air to cause an evolution ofentrapped gases, maintaining the alloy in a molten state until theevolutlon of gases substantially ceases, and recasting the material.

In witnesswhereof, I hereunto subscribe my name this 18th day of March,A. D., 1927. CARTER HENRY ANDERSON.

